Reversible space plane

ABSTRACT

A reversible aerospace plane includes an air intake at a first end of the aerospace plane, at least one heat exchanger disposed in the aerospace plane, an engine at a second end of the aerospace plane, wherein the aerospace plane is configured to accelerate in a first direction and configured to glide and land in a second direction, wherein the second direction is substantially in a reverse direction from the first direction.

This is a Continuation application of application U.S. Ser. No.11/040,170 filed Jan. 21, 2005 now U.S. Pat. No. 7,344,111.

BACKGROUND OF INVENTION

The loss of the space shuttle Columbia in 2003 highlights a need for asafer reusable single-stage-to-orbit (“SSTO”). The Columbia included apayload during re-entry, which was not typical for such re-entries. Inaddition to the mass of the payload, problems with the tiled heat shieldled to the catastrophic loss of the Columbia. Due to the shuttle'srelatively small footprint, structural weight, and rapid decent into theatmosphere, it dissipated most of the kinetic energy of orbital velocityin the denser atmosphere, relying exclusively on the heat shield toremain intact. Because of the need to clear the atmosphere relativelyquickly and reliance on boosters, the NASA space shuttle evolved into adaunting behemoth that is very costly to assemble and launch.

U.S. Pat. No. 5,191,761 (“the '761 patent”), owned by the applicant forthe present invention, discloses an air breathing aerospace engine. Thatpatent is incorporated by reference in its entirety. The engine includesa frontal core that houses an oxygen liquefaction system that capturesambient air and liquefies and separates the oxygen. The oxygen may thenbe used in the rocket engine.

U.S. Pat. No. 6,213,431 (“the '431 patent”) owned by the applicant forthe present invention, discloses an areospike engine. That patent isincorporated by reference in its entirety. An areospike engine may havea tapered body with a slanted or curved reaction plane. A fuel injectordirects fuel down the reaction plane. The combustion of the fuel on thereaction plane creates a propulsive force across the reaction plane.

What is needed, therefore, is a reversible re-usable SSTO vehicle thatmay be expediently launched to service the rapidly expanding spaceenterprise. A reduction in cost as well as an improvement in payloadcapacity are also desires of this growing industry.

SUMMARY OF INVENTION

In one aspect, the invention relates to a reversible aerospace planethat includes an air intake at a first end of the aerospace plane, atleast one heat exchanger disposed in the aerospace plane, and an engineat a second end of the aerospace plane, wherein the aerospace plane isconfigured to accelerate in a first direction and configured to glideand land in a second direction, wherein the second direction issubstantially in a reverse direction from the first direction.

In another aspect, the invention relates to a method of flying anaerospace plane that includes accelerating to an orbital velocity in afirst direction, re-orienting the aerospace plane, and re-entering anatmosphere in a second direction, wherein the second direction issubstantially in an opposite direction from the first direction.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a view of an ideal sphere moving at supersonic velocity.

FIG. 2 shows a cross section of an embodiment of an aerospace plane inaccordance with one embodiment of the invention.

FIG. 3 shows a schematic of a cooling/condensing system in accordancewith one embodiment of the invention.

FIG. 4A shows one embodiment of an aerospace plane in accordance withone embodiment of the invention.

FIG. 4B shows one embodiment of an aerospace plane with boosters inaccordance with one embodiment of the invention.

FIG. 4C shows one embodiment of an aerospace plane during re-entry, inaccordance with one embodiment of the invention.

FIG. 4D shows one embodiment of an aerospace plane prepared to land inaccordance with one embodiment of the invention.

FIG. 5 shows one embodiment of an aerospace plane with an aerospikeengine in accordance with one embodiment of the invention.

FIG. 6 shows one embodiment of an aerospace plane in accordance with oneembodiment of the invention.

DETAILED DESCRIPTION

An aerospace plane in accordance with one or more embodiments of theinvention may be a reversible aerospace plane. The aerospace plane mayinclude an air liquefaction system that enable the aerospace plane totravel at hypersonic velocities in the atmosphere with reduced drag.When operated in the reverse direction, the aerospace plane may exhibita larger drag so that the kinetic energy from an orbital velocity may bedissipated at a higher altitude and over a longer time period thanconventional vehicles.

FIG. 1 shows the ideal situation of a sphere 100 moving at hypersonicvelocity through the atmosphere. The surface 102 of the front half ofthe sphere 100 is an ideal condenser that will condense the incident airto a liquid upon contact with the surface 102. In this ideal model,instead of creating a shockwave in the atmosphere, the sphere 100condenses the air, thereby creating a partial vacuum in front of thesphere 100. The effect of this condensation of air is to reduce the dragexperienced by the sphere 100 to zero. The sphere can move at anunlimited speed through the atmosphere, without creating drag. Thisprinciple may be applied to the present invention to enable hypersonicvelocity at previously unattainable speeds.

FIG. 2 shows a cross section of an aerospace plane 200 in accordancewith one embodiment of the invention. The aerospace plane includes anose cone 201 at the front and a bell rocket engine 202 at the rear. Anair intake 204 allows air to flow into the aerospace plane 200 as itmoves through the atmosphere. The air enters a heat exchanger portion205 of the aerospace plane 200.

FIG. 3 is a schematic of a heat exchanger system 300 in accordance withone embodiment of the invention. Reference may be made to FIG. 2 aswell, to show the respective location of the components in thisparticular embodiment.

Air that is incident on the nose cone 301 (201 in FIG. 2) is cooled by acooling fluid in the nose cone 301. For a conventional aircraft, the airthat is incident upon the front of the aircraft as it moves through theatmosphere is compressed adiabatically. That is, the compression occurswithout substantial heat transfer. As a result, the incident airincreases in temperature. By cooling the air that is incident on thenose cone 301, the compression may be an isothermal compression. Thatis, heat is absorbed from the incident air so that it is compressedwithout a significant increase in temperature.

Generally, isothermal compression requires less energy that a similaradiabatic compression. Because of the lower energy requirement, there isless drag on the aerospace plane (200 in FIG. 2) as it travels throughthe atmosphere.

It is noted, however, that in practice, the incident air may experiencean increase in temperature. For example, incident air, which may have atemperature close to 0 degrees F. at altitude, may be heated to over1,500 degrees F. because of drag for a conventional aircraft travelingat about Mach 5. Precooling the air, as will be described, may result inthe incident air being heated to only 500 degrees F. Thus, thecompression process with precooling more closely approaches theisothermal ideal.

The precooling of the air before it flows through the intake (204 inFIG. 2) may be done using nitrogen gas (or liquid) separated from theincident air, as will be described. A heat exchanger 350 in the nosecone 301 may be used to pre-cool the air.

Upon flowing into the air intake 304 (204 in FIG. 2), the incident airenters a heat exchanger/condenser portion (205 in FIG. 2) of theaerospace plane. In the embodiment shown in FIG. 3, the incident air iscooled and condensed in three stages, 310, 320, 330. More or less thanthree stages may be used without departing from the scope of the presentinvention.

An aerospace plane in accordance with the invention may include ahydrogen tank 341 for storing an amount of hydrogen that is necessaryfor propulsion. The hydrogen it typically stored in liquid form, andtherefore, must be kept below −423 degrees F., the boiling point ofhydrogen. This liquid hydrogen must be evaporated before it may be usedas a propellant in the engine 302. To evaporate the hydrogen, it isconvenient to flow the hydrogen through heat exchangers (e.g., 310, 330in FIG. 3) so that cooling and condensing of the incident air may beaccomplished at the same time.

As shown in FIG. 3, hydrogen from the hydrogen storage tank 341 ispumped through the third stage heat exchanger 330, where the lowtemperature and the heat of vaporization are used to condense theincident air. As will be discussed later, in some embodiments, only theoxygen from the incident air is liquefied.

Hydrogen has a specific heat of 3.425 BTU/lb-degrees F. and a heat ofvaporization of 191.7 BTU/lb. Oxygen, on the other hand, has a specificheat of 0.219 BTU/lb-degrees F. and a heat of vaporization of 91.7BTU/lb. The greater values for hydrogen provide an advantage in coolingand condensing the oxygen.

Following the third stage, the hydrogen, typically in gaseous form,flows to the first stage 310, where it is used to continue the coolingprocess of the incident air following precooling from the nose cone 301.The hydrogen may then be pumped to the engine for use as a propellant orfuel. The incident air, following the precooling at the nose cone 301,flows through the air intake 304 (204 in FIG. 2) and into the firststage heat exchanger 310. In the first stage 310, the air cooled, andthe energy from the air is used to heat the hydrogen to an appropriatetemperature for combustion in the engine.

The cooling of the incident air continues in the second stage heatexchanger 320. In the embodiment shown in FIG. 3, the coolant in thesecond stage 320 is liquid oxygen, which may be from an oxygen tank 345or it may be the liquefied oxygen that results from the condensation ofthe oxygen in the air in the third stage 330.

In the third stage 330, at least a portion of the oxygen in the air isliquefied by giving up energy to the liquid hydrogen coolant in thethird stage 330. Air is mostly comprised of oxygen (about 20%) andnitrogen (about 80%). The boiling point of oxygen (i.e., thetemperature, at 1 ATM, below which oxygen is a liquid) is −180 degreesF. and the boiling point of nitrogen is −230 degrees F. This differenceenables the condensation of some or all of the oxygen in the incidentair, without liquefying any of the nitrogen in the incident air.

It is noted that the invention does not preclude the liquefaction ofnitrogen in the incident air. However, there may be certain advantagesto liquefying only the oxygen in the incident air. For example, coolingpotential needed to liquefy the nitrogen may be saved and used for otherpurposes, such as tanking additional oxygen. Also, liquefying thenitrogen in the incident air would require larger and more massive heatexchangers, which may adversely affect the available payload. Inaddition, the cooled nitrogen gas may be used for cooling purposes, aswill be described.

Following the third stage 330, the incident air may be separated into anoxygen component and a nitrogen component. The nitrogen component, shownat 323, may flow to the precooler heat exchanger 350 in the nose cone301 of the aerospace plane. The oxygen component may flow to the secondstage heat exchanger 320, where it may be evaporated into gas for use inthe engine 302. Additionally, the liquid oxygen from the incident airmay be pumped to a storage tank 345 for storage and later use—forexample, it may stored for use in space, where there is no atmosphere toprovide incident air.

Liquefying oxygen from the atmosphere during flight presents numerousadvantages. First, collecting and liquefying oxygen during flightgreatly reduces the amount of tanked liquid oxygen that must be storedon-board before lift off. A non-air breathing rocket must carry all ofthe oxygen that will be used during the entire flight. This represents asignificant mass. The hydrogen combustion reaction with oxygen requires2 moles of hydrogen for every mole of oxygen (H.sub.2O has two hydrogenatoms for every atom of oxygen). But because oxygen is 16 times heavierthan hydrogen, the required oxygen has 8 times the mass of the requiredhydrogen. In an air-breathing rocket, the oxygen may be distilled fromthe atmosphere, thus saving a substantial amount of mass.

Appendix A to this application includes two tables showing the amount ofpre-launch mass, including fuel and oxygen, that is required to propelone pound of payload into orbit. The fuel in this case is hydrogen. Thetwo cases are for a non-air breathing aerospace plane and an airbreathing aerospace plane. Starting with an orbital velocity of 25,000ft./sec, the chart shows calculations working backwards to zerovelocity. In each step, the difference in kinetic energy (DKe) is usedto determine the differential masses of the fuel (DH2, DO2) required toachieve the kinetic energy differential. The masses are thencumulatively added to the mass (MM) of the rocket.

The upper chart shows that for a non-air breathing rocket, 9.116 poundsof takeoff weight are required to get 1.000 pounds of payload to anorbital velocity of 25,000 ft./sec. The lower chart represents an airbreathing rocket. At velocities below 14,000 ft./sec, which representflight in the atmosphere, the differential in oxygen mass (DO2) is zero.This is because the oxygen may be condensed from the atmosphere, asdescribed above. The lower chart shows that only 5.183 pounds of takeoffweight is needed to propel 1.000 pound of payload to an orbital velocityof 25,000 ft./sec. For embodiments where a fraction of the liquefiedoxygen is tanked for later use, the required takeoff weight may be evenlower.

Appendix B shows similar charts for a rocket fueled with methane. Anon-air breathing rocket may require 23.941 pounds of takeoff weight topropel 1.000 pound of payload to an orbital velocity of 25,000 ft./sec,where an air breathing rocket may require only 10.572 pounds of takeoffweight. It is further noted that a hydrogen slush may be tanked, insteadof simple liquid hydrogen. A slush includes partially frozen hydrogenthat is still able to be pumped. This would increase the coolingcapacity of an aerospace plane by as much as 13%, resulting in a payloadincrease of as much as 10%. FIG. 4A shows a reversible aerospace plane400 in accordance with one embodiment of the invention. A reversibleaerospace plane is one that is capable of takeoff/acceleration in onedirection, but deceleration/re-entry and landing in a reverse direction.

The aerospace plane 400 includes a nose cone 401, and air intake 404,and a conventional bell rocket engine 402. In addition, the body of theaerospace plane 400 includes two wings 411, 412. During anacceleration/takeoff mode, the aerospace plane 400 may be propelled bythe engine 402 in the direction shown by the arrow 405. In thisdirection, the wings 411, 412 form a “hyper foil,” which is used to meanthat they present a small profile to the incident air, and the drag isminimized. The wings 411, 412 may form an air foil so that they willprovide lift during atmospheric flight. In addition, lift may begenerated by the angle of attack of the aerospace plane 400.

The nose cone 401 and the associated heat exchangers (e.g., 350 in FIG.3) may be constructed of a light and relatively inexpensive material sothat the nose cone 401 may be jettisoned from the aerospace plane 400before re-entry. During re-entry, the aerospace plane 400 may fly in anopposite direction, and the nose cone would no longer be needed. Theconstraints of heat exchanger design may require that the nose cone 401be formed in such a way that it would not be able to withstand theforces and heat of re-entry. In addition, a nose cone may present ahazard or obstruction during landing. Thus, it may be jettisoned fromthe aerospace plane 400, as will be explained.

The aerospace plane 400 in FIG. 4A may be used with a piggy-backarrangement to gain an initial altitude and airspeed. For example, alarger plane may be used to carry the aerospace plane 400 from theground to an altitude of 30,000 ft.-50,000 ft. From this point, the bellengine 402 may be engaged to provide the thrust to achieve orbit.

FIG. 4B shows an aerospace plane 420 with solid rocket boosters 421,422, similar to the boosters that have been used with the NASA spaceshuttle orbiter. The boosters 421, 422 may be used to provide lowaltitude thrust for the aerospace plane 420. The boosters 421, 422 maybe jettisoned once they have been spent.

FIG. 4C shows one embodiment of a reversible aerospace plane 430 duringa re-entry phase. The aerospace plane 430 is flying in a reverseorientation from the aerospace planes 400, 420 shown in FIGS. 4A and 4B.This may be accomplished by simply using orientation thrusters to rotatethe aerospace plane 430 180 degrees while in orbit and before re-entrybegins. In FIG. 4C, the nose cone (401 in FIG. 4A) has been jettisoned.In addition, at the forward section of the aerospace plane 430 in thismode, the engine (402 in FIG. 4A) has been likewise jettisoned foraerodynamic control purposes.

The aerospace plane 430 and its wings 431, 432 are formed so that in thereverse direction, they create a “para foil”—that is, they are formed tohave rounded edges that present a large profile and create more dragthat when the aerospace plane 430 flies in the takeoff direction (e.g.,the direction shown in FIG. 4A). As shown in FIG. 4C, the aerospaceplane 430 may be pitched upwardly so as to create even more drag.

The drag on the aerospace plane 430 in the reverse direction enables theaerospace plane 430 to dissipate a large amount of kinetic energy in theupper atmosphere, where atmospheric density is low enough so that theaerospace plane 430 will not generate temperatures that requiresophisticated heat shielding.

For example, the NASA space shuttles will generally re-enter the denseatmosphere at very high speeds. The space shuttle will slow to normalair velocities within about a quarter of a full orbit. For example, whenlanding in Florida, it is typical for a space shuttle to begin slowingdown at a position near Hawaii. The shuttle will then slow down and landin the distance between Hawaii and Florida.

An aerospace plane 430 in accordance with the invention may have asufficient drag so that slowing down may be accomplished at a muchhigher altitude and over a longer distance. For example, an aerospaceplane 430 may slow from orbital velocity over two complete orbits aroundthe Earth, taking a much longer time. The additional time enables theaerospace plane 430 to dissipate the heat associated with slowing downso that sophisticated heat shielding is not required. Further, thestructure and required propellant of such an aerospace plane may enableit to be substantially lighter than previous vehicles. A reduction inmass will also reduce the kinetic energy that must be dissipated duringre-entry.

It is noted that an aerospace plane in accordance with the invention maybe referred to a traveling in a “reverse direction.” In practice, anaerospace plane may be oriented in a reverse situation, even though thevector of travel for the aerospace plane has not itself reversed. Theuse of “reverse direction” is meant to indicate a reverse orientation ofthe aerospace plane.

FIG. 4D shows the aerospace plane 430 in a maneuvering/landing mode. Theaerospace plane 430 is pitched downward for gliding, maneuvering, andlanding. The wings 431, 432 may form an airfoil to generate lift thatwill aid in the maneuverability of the aerospace plane 430. It is alsonoted that an aerospace plane in accordance with the invention may bemanned or unmanned. A remotely controlled aerospace plane may be usedwhile still gaining the advantages of the present invention. A mannedaerospace plane is also within the scope of the invention. The reducedtemperatures during re-entry provide a significantly safer re-entryphase than with the existing space shuttle design.

FIG. 5 shows another embodiment of an aerospace plane 500 in accordancewith the invention. The aerospace plane 500 includes a nose cone, andair intake 504, and wings 511, 512, as the embodiment shown in FIG. 4A.The illustrated difference is that the aerospace plane 500 in FIG. 5includes an aerospike engine 502 instead of a bell nozzle. An asonicaerospike engine is disclosed in U.S. Pat. No. 6,213,413 (“the '413patent”), which is owned by the applicant for the present invention.That patent is incorporated by reference in its entirety.

The aerospike engine 502 shown in FIG. 5 includes a primary reactionplane 521, and two secondary reaction planes 522, 523. Any arrangementof reaction planes may be devised for an aerospike engine with outdeparting form the scope of the invention.

As disclosed in the '413 patent, an aerospike engine is able to operatemore efficiently than a bell nozzle at a variety of altitudes. Becauseof this feature, an aerospace plane 500 with an aerospike engine 502 maybe able to takeoff on a runway, using the thrust from only the aerospikeengine. In this regard, an aerospace plane 500 forms a self-sufficientSSTO vehicle that may take off from a runway, achieve an orbitalvelocity, orbit the Earth, re-enter the Earth's atmosphere in a reversedirection, and land. Advantageously, such an aerospace plane 500 may notrequire the use of boosters or a piggy-back.

FIG. 6 shows another embodiment of an aerospace plane 600 in accordancewith the invention. The aerospace plane 600 does not include a nosecone. Instead, the entire aerospace plane forms a wing-type structure,and there is an air intake 604 at a first end of the aerospace plane600. An engine 602 is located at the other end, and in the embodimentshown in FIG. 6, the engine 602 is an aerospike engine. The aerospaceplane 600 is shown with boosters 611, 612 that may be jettisoned. Insome embodiments, and aerospace plane 600 does not include boosters. Forexample, an aerospace plane 600 may include an aerospike engine 602 thatenables the aerospace plane 600 to takeoff, fly to orbit, and landwithout the need for boosters. Additionally, a piggyback may be used.

In a takeoff/acceleration mode, the aerospace plane 600 travels in afirst direction 605. Incident air flows into the air intake 604, and isthen cooled and condensed, thereby reducing the drag on the aerospaceplane 600 at hypersonic velocity. The engine 602 may be used to propelthe aerospace plane 600. Upon reaching orbital velocity, the air intake604 may be closed. For a re-entry/deceleration/landing mode, theaerospace plane 600 may travel in a reverse direction 606. The engine,which may be a bell nozzle in some embodiments, may be jettisoned. Anaerospike engine may be adapted to withstand the forces and temperaturesof re-entry, or an aerospike engine may be retracted for re-entry.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

1. A reversible aerospace plane, comprising an air intake at a first end of the aerospace plane to receive air; at least one heat exchanger disposed in the aerospace plane; and an engine at a second end of the aerospace plane, wherein the aerospace plane is configured to accelerate in a first orientation and configured to glide and land in a second orientation, wherein the second orientation is substantially a reverse of the first orientation, said at least one heat exchanger comprising a plurality of stages, at least one stage of said plurality of stages being configured to use tanked liquid hydrogen as a coolant to condense at least a portion of an oxygen component of the received air to produce liquefied oxygen and another stage of said plurality of stages being configured to condense the received air through the expansion of said liquefied oxygen produced in said at least one stage of said plurality of stages.
 2. The reversible aerospace plane as defined in claim 1, in which said plurality of stages further comprises an intake heat exchanger stage to cool the received air through the expansion of nitrogen separated from said received air.
 3. The reversible aerospace plane as defined in claim 2, in which said reversible aerospace plane includes a nose cone, further comprising a nose cone heat exchanger disposed in the nose cone and configured to pre-cool incident air.
 4. The reversible aerospace plane as defined in claim 3, wherein the nose cone is configured to be jettisoned before a re-entry.
 5. A reversible aerospace plane, comprising an air intake at a first end of the aerospace plane to receive air; at least one heat exchanger disposed in the aerospace plane; and an engine at a second end of the aerospace plane, wherein the aerospace plane is configured to accelerate in a first orientation and configured to glide and land in a second orientation, wherein the second orientation is substantially a reverse of the first orientation, said at least one heat exchanger including a plurality of heat exchanger stages, said plurality of heat exchanger stages comprising: (a) one stage configured to condense the received air through the expansion of tank hydrogen; (b) another stage configured to condense the received air through the expansion of oxygen separated from condensed air in said one stage; and (c) an intake heat exchanger stage to cool the received air through the expansion of nitrogen separated from air condensed in said one stage.
 6. The reversible aerospace plane has defined in claim 5, wherein the engine comprises a bell nozzle engine.
 7. The reversible aerospace plane as defined in claim 5, wherein the bell nozzle engine is configured to be jettisoned before a re-entry.
 8. The reversible aerospace plane as defined in claim 5, wherein the engine comprises an aerospike engine.
 9. The reversible aerospace plane as defined in claim 5, wherein the aerospace plane forms a hyper foil when traveling in the first orientation and a para foil when traveling in the second orientation. 